Rail and Maritime Transport Union Organiser John Kerr says it's all about safety.

"Auckland Transport and Transdev want to take train managers off the trains and our members are saying that's going to compromise public safety and they're not prepared to do that.

"[Train managers] are first responders in the event of an emergency, they do crowd management and they're also operational, so if there's a signals failure they intervene. They're really a critical member of staff."

He says without train managers on board, passenger safety is in serious jeopardy.

"There'll be an increase in antisocial behaviour and also an increased risk of 'platform train interface incidents' in other words people getting hurt because they're getting dragged under the train or they're stuck in the door."

Train managers will be replaced with a larger team of roving transport officers who will be trained to manage anti-social behaviour and have flexibility to move around.

Mr Kerr says this would get rid of around 180 train managers, as well as additional platform staff, in what some are calling a cost-cutting measure.

"They say they'll introduce these roving transport officers, but they don't have as much power as the train managers and there won't be one on every train.

"If your daughter is going home late at night, there's no guarantee that there would be a uniformed presence on that train apart from the driver who's locked in the cab. We're saying that's just not acceptable."

Mr Kerr says he understands this industrial action is not the ideal outcome, but it has to happen.

"We don't want to inconvenience the public, we know this is going to be an inconvenience, but we're not prepared to compromise on public safety."

He says he was surprised Auckland Transport put on a reduced timetable in response to the industrial action.

"We didn't anticipate [that]. We knew the network runs on overtime - that's what this is, an overtime ban - and that in itself is an indictment of AT and Transdev's poor management, that they don't have a network that can be run fully staffed."

Rail and Maritime Transport Union representatives will meet with Auckland Transport and Transdev on Wednesday.

Transdev Managing Directing Michel Ladrak says the company is working to end the industrial action as quickly as possible.

"We believe Aucklanders want the safest and most enjoyable train journey and we are working with Auckland Transport to achieve this," he said in a statement.

"It is incorrect for John to suggest that train drivers will be solely responsible for passenger assistance and security. Closing train doors is only one part of a very comprehensive series of safety controls.

"Antisocial behaviour can be experienced by anyone, anywhere, at any time. On board, it cannot be effectively targeted by a lone train manager."

Mr Kerr says if progress is made in Wednesday's meeting, the union will pull its overtime ban.

"We don't want to do this but we're not going to compromise on passenger safety."